1. Field of the Invention
The present invention relates to apparatus for measuring the wall thickness of tubes, said apparatus comprising at least one measuring body which bears resiliently against the inner wall surface of the tube and which reacts upon a measuring device arranged externally of the tube wall.
2. Reference to Prior Art
Measuring devices of this kind are already known, see for example DT-OS No. 2,260,468. In the known device the measuring body is selectively applied to or removed from the inner wall surface by means of an electromagnet by external control. Apart from the fact that the necessity for having an electrical control line renders the construction comparatively complicated, this known construction also demands external arbitrary control.